Whether a farmer is growing in an organic or conventional system, his or her crop needs to be protected from damage from plant pests (insects, fungi, bacteria, viruses, nematodes, weeds…). To fail to minimize pest damage leads to inefficient use of scarce resources like prime farm land, water, or inputs. The quality and safety of the final products can also be compromised.
While materials we think of as “pesticides” play an important role, modern agricultural pest management depends on a combination of several tools and strategies which, when used together, offer a more resilient, economic, and effective means of crop protection. Though some of these practices have been part of traditional farming, many are more recent innovations. The explicit design of these multi-strategy programs began in the 1970s, and the approach is now widely adopted as integrated pest management (IPM). The optimal IPM program varies widely by crop and geography; this post will describe some examples that highlight the various components.
The approaches used to implement IPM programs generally fall into six categories:
- Avoiding the pest
- Employing the plant’s own genetic defenses
- Modifying the climate
- Disrupting the pest’s life cycle
- Fostering beneficial organisms
- Using targeted pesticide applications
A brief introduction to each of the six approaches follows with additional links to the more detailed presentations. Each post will link back to the list above.
Not all pests occur in all places either because they have not spread there or because they cannot flourish in the climate of a given region. Both of these limitations have been historically important factors to consider when deciding what crops to grow where, and these pest limitations continue to be important considerations for farmers. Long-term, this strategy is limited by climate change and by the extensive movement of people and goods around the world
Plants fight back against pests by evolving a variety of defensive strategies controlled by genetic traits. Built-in genetic resistance is an attractive form of pest control for farmers, but it is a resource that requires considerable effort to employ and stewardship to maintain as an effective part of an IPM program. For some crops, farmers can maintain a seed bank of genetic variation and draw upon it to keep ahead of the pest’s inevitable tendency to evolve around plant defenses.
When genetic resistance is available, it is generally wise to complement it with other IPM elements, such as pesticides, to avoid losing the valuable traits. For many crops, conventional methods of breeding are too slow and/or complex to easily employ genetic solutions. Traditional and advanced grafting approaches offer a dual plant genetics approach that has been quite useful in many systems. Advancements in biotechnology allow farmers to use same-species resistance genes in hard-to-breed crops as well as novel genetic approaches that have shown considerable benefit in the few cases where they have been allowed to-date.
In some cases, farmers can shift the microclimate in which the plant is grown enough to reduce the threat of certain pests. Various degrees of protected culture have been widely used to shield crops from rain and/or to shift the temperature regime to extend the growing season at either end. The nature of the plant canopy can sometimes be managed to reduce humidity, increase light or otherwise create a microenvironment that is suppressive to certain pests.
Several strategies for pest control center on making it more difficult for the pests to reproduce. These range from crop rotation to insect pheromones to removal of damaged or infested plant parts. Other approaches involve the release of male insects which are sterile so that the females with which they mate do not produce any offspring.
Even pests have pests, and often there are ways that farmers can encourage these natural enemies to help keep pest populations low enough to obviate the need for other control measures. Sometimes, it is possible to actively produce and add the bio-control organisms to the system.
Farmers can use a wide range of crop protection agents as part of an IPM system. In a great many cases, these agents are low hazard options in terms of environmental, beneficial, or human impact, but the use of all such agents is highly regulated on a national and state level. These crop protection agents are often important for preserving the utility of other IPM approaches, particularly genetic resistance. Farmers have many economic and practical incentives to only use these materials on an as-needed basis.
Pest control in agriculture is a multi-dimensional effort, and pesticides are just one of the important tools that farmers employ. Some of these tools have been in use for a long time and some are new. With climate change, the control of pests will become even more difficult. As the global population grows and standards of living increase, it will be even more important for farmers to avoid the sort of losses and food waste that pest cause. Fortunately, the toolbox available to fight pests is diverse and constantly improving.
Steve Savage is an agricultural scientist (plant pathology) who has worked for Colorado State University, DuPont (fungicide development), Mycogen (biocontrol development), and for the past 13 years as an independent consultant. His blogging website is Applied Mythology. You can follow him on Twitter @grapedoc